Fabrication of carbon nanotubes-polyaniline composite thin films using layer-by-layer technique for gas sensing application

Abstract

In this study, we have used anionic and cationic multi-wall carbon nanotube polyelectrolytes, prepared by the noncovalent surface modification of water soluble polyabiline and polydiallydimethylamonium chloride on nanotube sidewall, for the layer-by-layer self assembly to prepare multilayers from carbon nanotube with polycation such as polydiallydimethylamonium chloride, and polyanion such as poly(sryrenesulfonate) or water soluble polyabiline, respectively. The multilayer composite thin films are constructed by alternating of anionic and cationic polyelectrolyte. This is a general and powerful technique for the fabrication of thin carbon nanotubes films of arbitrary composition and architecture and allows also an easy preparation of all composite films. On the other hand, water soluble polyaniline was designed and synthesized for use as polyelectrolytes. The water soluble polyaniline was prepared by interfacial polymerization of aniline monomer in presence of poly (styrene sulfonate). The composite multilayer thin films were characterized for their optical and electrical properties. The electrical properties of the films were measured using a 4 point probe setup and the optical properties were measured by UV-Vis spectroscopy. The thickness and surface of the film was measured by atomic force microscopy. The charge compensation in multilayers is mainly intrinsic, which shows the electrostatic nature of the self assembly process. The CNT present in the composite film improve its conductivity and allow the fabrication of sensor which can be used both as an optical and electrical. This composite of polyelectrolyte, CNT and polyaniline is a promising composite film for gas sensing.